The present invention relates to a head suspension assembly (HSA) or a head gimbal assembly (HGA), with a precise positioning actuator for a thin-film magnetic head element used in a magnetic hard disk drive (HDD).
In the magnetic HDD, thin-film magnetic head elements for writing magnetic information into and/or reading magnetic information from magnetic disks are in general formed on magnetic head sliders flying in operation above the rotating magnetic disks. The sliders are supported at top end sections of suspensions of the HSAs.
Recently, either recording and reproducing density along the track direction in the magnetic disk (bit density), or recording and reproducing density along the radial direction or along the track width direction in the magnetic disk (track density) rapidly increase to satisfy the requirement for ever increasing data storage capacities and densities in today""s HDDs. Also, the requirement for high data rate in the HDDs increases and thus improvement in the speed of the disk rotation is advanced.
For advancing the bit density, because of a long distance between a head drive circuit and a thin-film magnetic head element, floating noises generated in the wiring for connecting the drive circuit with the head element have become a big problem. Also, for advancing the track density, the position control of the magnetic head element with respect to the track in the magnetic disk by a voice coil motor (VCM) only has never presented enough accuracy.
In order to solve the former problem, a drive IC (integrated circuit) chip having a part of the drive circuit of the magnetic head element is mounted on a suspension. Also, in order to solve the latter problem, another actuator mechanism is mounted at a position nearer to the magnetic head slider than the VCM so as to perform fine precise positioning that cannot be realized by the VCM only. The latter techniques for realizing precise positioning of the magnetic head are described in for example U.S. Pat. No. 5,745,319 and Japanese unexamined patent publication No. 8-180623.
However, even if either the bit density or the track density is advanced, it is very difficult to satisfy the recent requirement for further increased data storage densities in the HDDs.
It would have been considered that the mounting of both of the IC chip and the additional actuator on the same suspension more improve the data storage densities. However, if they are mounted together on the suspension, the following problems have occurred.
(1) The number of trace conductors formed on the suspension is greatly increased. In a typical magnetic head, for example a composite type magnetic head with a read head part of a magnetoresistive effect (MR) transducer element and a write head part of an inductive transducer element, four or more trace conductors are required for reading and writing operations and two or more additional trace conductors are required for driving the additional actuator. Thus, it is necessary to make six or more trace conductors on the suspension. That is twice of that in the conventional HSA. If the number of the trace conductors running on the suspension increases, noises due to the floating capacitance of the trace conductors may affect the read/write signals, and/or heat may be considerably generated on the suspension.
(2) Comparatively high voltage is required to drive the actuator. However, since the suspension has the IC chip on its middle section, it is very difficult to design a wiring of the HSA and a circuit of the HDD so as to form trace conductors for providing such high voltage to the actuator located at the top end section of the suspension from the HDD along the whole length of the suspension.
Thus, conventionally, the IC chip and the additional actuator never have been mounted together on the same suspension.
In addition, if a piezoelectric material type actuator is used, poor resistance to shock will become a large problem. Namely, such piezoelectric material type actuator may be physically broken and/or depolarized easily if a shock is applied in the direction that intersects its plane when a voltage is applied thereto.
It is therefore an object of the present invention to provide a HSA, whereby requirement for further increased data storage densities in HDDs can be sufficiently satisfied.
Another object of the present invention is to provide a HSA, whereby the number of trace conductors formed on a suspension can be reduced.
Further object of the present invention is to provide a HSA, whereby a wiring design of the HSA and a circuit design of a HDD can be easily carried out.
Still further object of the present invention is to provide a HSA, whereby physical breakage of and/or depolarization in piezoelectric material of an actuator by the shock can be effectively prevented even if a piezoelectric material type actuator is used.
According to the present invention, a HSA includes a magnetic head slider with at least one thin-film magnetic head element, an actuator fixed to the magnetic head slider for performing precise positioning of the at least one thin-film magnetic head element, an IC chip having a first circuit for the thin-film magnetic head element and a second circuit for driving the actuator, and a suspension for supporting the actuator and the IC chip.
Since both the IC chip and the actuator are mounted on the suspension, it is possible to increase the bit density and the track density together and therefore requirement for further increased data storage densities in HDDs can be sufficiently satisfied. Also, since the second circuit for driving the actuator is formed in the IC chip mounted on the suspension, the number of trace conductors formed on the suspension can be reduced. Thus, noises generated from the trace conductors, which will adversely affect the read/write signal of the magnetic head element, can be reduced from occurring, and heat generation due to current flowing through the trace conductors on the suspension can be also reduced.
It is preferred that the first circuit includes an amplifier circuit for amplifying a read signal from the at least one thin-film magnetic head element, and an amplifier circuit for amplifying or driving a write signal to the at least one thin-film magnetic head element.
It is also preferred the second circuit includes a first control circuit for producing a positioning signal depending upon the read signal from the at least one thin-film magnetic head element, and a booster circuit for boosting the produced positioning signal to produce a drive signal used for driving the actuator. Since such the booster circuits are also formed in the IC chip mounted on the suspension, the drive signals with a comparatively high voltage for the actuator will pass through only the conductors provided between the IC chip and the actuator resulting that a wiring design on the suspension becomes easy. In addition, since it is no necessary to generate such comparatively high voltage signals at the HDD, a circuit design of the HDD becomes easy and further its specification becomes simple.
Preferably, the read signal from the at least one thin-film magnetic head element is a servo signal generated at the at least one thin-film magnetic head element by reading out servo information preliminarily recorded on a magnetic disk.
It is preferred that the IC chip includes a third circuit for protecting the actuator from physical breakage and/or depolarization due to a shock applied thereto. In this case, the third circuit will include an impact detection circuit for detecting shock applied thereto, and a second control circuit for stopping supply of the drive signals to the actuator when the impact detection circuit detects the shock. Since the impact detection circuit is formed in the IC chip mounted on the suspension, a shock applied to the actuator mounted on the same suspension can be directly detected and application of the voltage to the actuator can be stopped by the second control circuit on timing. Therefore, physical breakage and/or depolarization of the actuator by the shock can be effectively prevented even if a piezoelectric material type actuator is used.
It is preferred that the actuator and the IC chip are located on one surface of the suspension. This one surface of the suspension may be a surface faced to a magnetic disk surface in operation.
It is also preferred that the HSA further includes a first conductor member with one end electrically connected to the at least one thin-film magnetic head element and the other end electrically connected to the IC chip, a second conductor member with one end electrically connected to the actuator and the other end electrically connected to the IC chip, and a third conductor member with one end electrically connected to the IC chip and the other end electrically connected to connection pads to be connected to an external circuit.
Preferably, the one end of the first conductor member is directly connected to terminals of the at least one thin-film magnetic head element by ball bonding or by stitch bonding.
It is further preferred that the first, second and third conductor members are formed by flexible print circuits with trace conductor layers sandwiched by insulation layers.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.